A conventional method for operating a three-step inverter includes an inverter having an intermediate circuit with two capacitors from whose connecting point a measuring resistor is connected to the ground. A voltage drop in the measuring resistor while the converter is operating is measured. Depending on this measured voltage, it is determined whether a ground fault is present in the inverter.
One disadvantage of the known method is that a ground fault already present before the inverter's initial operation can only be determined when it is operating and this can damage the inverter. Therefore, an improved method for determining whether a ground fault is present in the electrical circuit that prevents damage to the inverter would be useful.